He also has three sisters, and another half-brother. He attended his father's funeral at Forest Lawn in 1970 with his sisters, and is significantly younger than his half-brother, Bosch. While Bosch was an adult upon meeting their father, Mickey was only five years old when the elder Haller died. Little is known of Haller's childhood other than the death of his father at a young age, and his inheritance of his father's Colt Woodsman .22 pistol.

Like his father, he is a criminal defense attorney in Los Angeles, and is a staunch opponent of the death penalty, claiming that "an enlightened society [does] not kill its own." He is from a family of attorneys. In addition to his father, other lawyers in the family include his half-brother, a niece and a nephew. He has conflicted thoughts and emotions about defending criminals. Although he frequently tells people that it doesn't matter if his clients are guilty or innocent, his inner thoughts betray an intense concern with that question. He appears much more comfortable defending clients that he knows are guilty.

As a public defender in 1992, Haller represented Barnett Woodson and won acquittal against prosecutor Jerry Vincent, who subsequently left the District Attorney's office to open his own defense practice. In 1993, he represented Raynard Waits in a prowling charge, negotiating a plea agreement that gave his client an eighteen month probation sentence. Later in the year, Haller married prosecutor Margaret McPherson, and in 1995, he left the Public Defender's office to open his own private defense firm. During that time they lived in a condo on Dickens Street in Sherman Oaks. He and McPherson had a daughter, Hayley Haller, in 1997, but subsequently divorced in 2001 while remaining amicable. After their divorce Haller moved out of the condo and bought a house on Fareholm Drive in the Hollywood Hills. In the wake of his divorce, Haller married his own case manager, Lorna Taylor, but that marriage ended quickly as well when the two divorced in 2002. In general, Haller is not very good at understanding or dealing with women.

As a defense attorney in private practice, Haller preferred to not have a permanent office, opting instead to work out of his car. He has had a series of Lincoln Towncars, leading to his moniker The Lincoln Lawyer. He sometimes drives himself but more often has employed several drivers including Earl Briggs, Patrick Henson, and Rojas. His business phone number is 323-988-0761, which rings at Lorna Taylor's condo. Since Haller works out of his car, Taylor's condo on Kings Road in West Hollywood has most often been the closest thing to a permanent office for the law firm.

Haller has employed the services of two private investigators for his trials. The first, Raul "Mish" Levin, was murdered in April of 2005; his nickname "Mish" was bestowed upon him by Haller after learning of his mixed Mexican-Jewish ancestry. His second investigator, Dennis "Cisco" Wojciechowski, was hired after Levin's death, and dated Lorna for a year before proposing to her in November of 2007.

In 2003, Haller represented Jesus Menendez after Menendez was arrested for the rape and murder of stripper Martha Renteria. The prosecution had DNA evidence and witnesses who said they saw Menendez throw a knife into the L.A. River. Haller convinced Menendez to accept a plea deal that would incarcerate him for life in order to prevent the prosecution from seeking the death penalty, and Menendez eventually agreed despite insisting on his innocence. He was serving his sentence at San Quentin State Prison. Haller said this was his twelfth murder trial and all twelve were in prison, but none were on death row.

In March of 2005, Haller represented Louis Roulet after Roulet was arrested for the attempted rape and attempted murder of escort Regina Campo. In the process of investigating the case in order to build Roulet's defense, Haller discovered important similarities to the Menendez case, and Haller's private investigator Raul Levin found a parking ticket that put Roulet on Renteria's street the night she was killed. Roulet broke into Haller's house and stole his Colt Woodsman pistol. Levin was murdered with that gun before he was able to pass the parking ticket information on to Haller. After Levin's murder, Haller knew that his client was guilty of the assault on Campo and the murder of Renteria, presenting him with a tough ethical dilemma. He resolved this by devising a strategy that would acquit Roulet in the current case while setting him up for prosecution in the Renteria case and thereby clearing Menendez. The strategy consisted of having Gloria Dayton talk to a secret prosecution witness who was in a lockup drug rehab with her. Haller couldn't be sure this secret witness would even be called, so he pushed the prosecution hard to make it happen.

Prosecutor Ted Minton, fearing that his case was weak, called the secret witness to testify against Roulet. The witness falsely claimed that Roulet had confessed to him that he had assaulted Campo, but he also mentioned details related to the Renteria murder as he had been instructed by Haller via Dayton. It is not clear whether Haller had offered the witness money for this additional testimony, but it seems likely. After exposing that the witness had lied in a previous case in Phoenix, Haller succeeded in getting the D.A.'s office to drop all charges against Roulet, but the witness's mention of the Renteria case was enough to get the attention of LAPD detectives. Roulet was released in the Roulet case but then immediately arrested by detective Howard Kurlen for the Renteria murder.

Later that night, Roulet was released again in a police plan to use Haller as bait, believing that Roulet would try to kill him next. Instead, Roulet went to McPherson's apartment and was arrested there. Roulet's mother, Mary Windsor, went to kill Haller using the stolen Colt Woodsman. Windsor shot Haller in the stomach but he shot back, killing her just as detectives arrived.

All did not go well for Haller afterwards. Menendez was subsequently released from prison and sued Haller for legal malpractice. He learned that Menendez contracted HIV in prison, and guilt about his handling of Menendez's case weighed heavily on him. In addition, he was sanctioned by the bar for Conduct Unbecoming an Attorney. On the positive side he felt good about getting Menendez out of prison and getting Roulet into prison.

Haller suffered a hernia as a result of his gunshot wound, and underwent surgery to correct the protrusion. The surgery went poorly, however, and Haller successfully sued the hospital for medical malpractice. Following his surgery, he became addicted to OxyContin, and eventually checked into the Laurel Canyon Recovery Center in 2006 to kick his habit. His legal practice was dormant for a year.

In November of 2007 when Haller was preparing to resume work, he was summoned to the chambers of Judge Mary Holder and informed that fellow criminal defense attorneyJerry Vincent had been murdered, and that Haller had thereby inherited Vincent's law practice, which amounted to 31 clients including film producer Walter Elliot. Harry Bosch, was lead investigator in Vincent's murder. The Elliot case was a huge opportunity for Haller with a potential fee of $250,000. Another client he picked up was Patrick Henson who he hired as a driver. He retained Cisco as his full-time investigator.

As he came up to speed on the Elliot case, he learned that Vincent believed he had a "magic bullet" for the defense but he left no information about this in his files. While Haller was focused on the Elliot case, he was also concerned about the murder of Vincent. He could not allow Bosch direct access to Vincent's files, but he provided what information he could, mainly in regards to clients who had made threats against Vincent. Bosch looked into these and ruled them out. Haller then learned that Vincent had a mysterious pro bono client, Eli Wyms, with no file and a strange case history. Haller realized the Wyms could have been the "magic bullet." Vincent had already lined up a national expert on gunshot residue, Dr. Shamiram Arslanian, and she became the key witness in Haller's defense strategy.

Two things blew the Elliot case wide open. First, Cisco's investigations revealed that Juror number 7, David McSweeney, was not who he claimed to be. Haller wrote an anonymous note to Judge Stanton to that effect. Secondly, Elliot admitted his guilt to Haller during a dinner meeting at the Water Grill. The outcome was that Elliot and Nina Albrecht were killed by the family of Johan Rilz, making the trial moot. Hours later, McSweeney tried to kill Haller but was arrested by Bosch and FBI agents.

Haller realized that both the jury fix and the murder of Vincent had been a conspiracy engineered by Judge Holder and her husband. He was thoroughly disenchanted with law and decided he would quit. He also realized that Bosch was his half brother, a fact that Bosch had known for some time.

In his private life, Haller continued to try to improve his relationship with his ex-wife. His daughter stayed with him on Wednesdays and every other weekend. On Wednesday nights they would go to Dupar's Restaurant, and she always ordered pancakes. However, Hayley wished that her dad was putting bad people in jail instead of getting them out.

In September of 2009, Haller was contacted by Harry Bosch to serve as the detective's personal lawyer when investigators with the Hong Kong Police Force questioned him about the shooting of Eleanor Wish at the Chungking Mansions and the murder of the Qingcai family. He helped dissuade the detectives from taking any action against Bosch, stating "what happens in Hong Kong stays in Hong Kong." When Bosch offered to pay him for his representation, Haller declined and suggested to Bosch that Hayley and Madeline should meet, but Bosch stalled on the proposition.

On 9 February 2010, Haller was approached by Gabriel Williams and offered the opportunity to prosecute recently-released Jason Jessup in a retrial for the 1986 murder of 12-year-old Melissa Landy. This would be a tricky assignment because Jessup's original conviction had been overturned based on DNA evidence. In addition, the new jury must not be aware that there had been a previous trial or that Jessup had been in prison. Haller accepted the job on the condition that McPherson serve as his second chair (and that McPherson get transferred from the courthouse in Van Nuys to the District Attorney's office downtown if Jessup was reconvicted) and LAPD detective Harry Bosch serve as his investigator. He was opposed by defense attorney Clive Royce before Judge Diane Breitman. Haller immediately took control of the case by not opposing bail for Jessup, which infuriated both McPherson and Williams.

The trial proceed smoothly until the final day, 8 April, when Haller and Bosch teamed up to destroy defense witness Edward Roman. After Jessup killed four people and was then killed by police, Haller was overcome with guilt and self-doubt because he had not opposed bail for Jessup. Furthermore, he learned that Juror number ten (Kirlin) was telling the media that he would have voted to acquit, which would have allowed Jessup to go free. On the positive side, this case brought Haller and Bosch closer together and allowed their two daughters, Hayley and Madeline, to meet and become friends.

Haller believed Trammel was probably guilty and he did not like her, but he had to defend her. His strategy was to suggest a "straw man", i.e. a different killer and motive. He chose Louis Opparizio who fit the bill perfectly. Haller had some success with other witnesses, but when he called Opparizio to testify he hit a home run. After answering a few warm-up questions. Opparizio "took the nickel" and refused to testify, creating more than enough doubt in the jury to get his client acquitted. Haller even started to believe his own theory, that Opparizio had Bondurant killed to prevent problems with the sale to LeMure. Afterwards Haller realized that his client was guilty after all. She had also hired the thugs to beat Haller, and she had probably killed her own husband. When Trammel called Haller to say she was going to be arrested for the murder of her husband, Haller told her to find a new lawyer. Then Haller told McPherson that he was thinking of running for District Attorney.

In April of 2011, Haller filed to run for the office of District Attorney of Los Angeles. Gabriel Williams had been appointed to a high ranking position in the Attorney General's Office. But in 2012, Haller lost the race for D. A. to Damon Kennedy, "in scandal and self-destruction" when a former client, who had previously escaped a DUI charge under Haller's representation, killed two pedestrians (Sandy and Katie Patterson) and himself. Even worse, his daughter refused to see him because Katie Patterson had been her friend. He later sought out his father's former law partner and strategist, David Siegel, for help in dealing with his guilt.

On Tuesday 13 November 2012, Haller was in court for the trial of Leonard Watts, charged with carjacking. When it became clear that Haller had made no dent in the prosecution's main witness, they staged a pre-rehearsed fight in order to force a mistrial. Haller's strategy was to get the prosecutor to make a deal rather than go through another trial. Later that day Haller was contacted by Andre La Cosse, who was accused of murdering a high-end escort. Haller accepted the case when he discovered that the murder victim was his own former repeat client Gloria Dayton who had changed her name to Giselle Dallinger. La Cosse was her website manager and digital pimp.

At this time Haller had an office of sorts, a loft space in a building on Santa Monica Boulevard that was going through foreclosure. Haller was representing the building owner in exchange for use of the space. Haller always wants to know how he will be paid, and in this case La Cosse paid him in gold bars. As with other cases, Haller set out to develop a "straw man" defense, suggesting that the killer was someone else. This time Haller became convinced that La Cosse was innocent and someone else had actually killed Dayton. He set out to understand who and why.

With the vital assistance of Cisco and some surveillance video, he learned that someone was tailing Dayton the night she was killed. Cisco got a license plate number from a car belonging to Lee Lankford, an investigator from the D.A.'s office. Seemingly out of left field, Haller was subpoened by Sylvester Fulgoni, Jr. who was representing Hector Arrande Moya. Haller learned that subpoenas were also being served on Kendall Roberts and a DEA agent named James Marco. These subpoenas told him who the major players were. As more evidence came in, he discovered that these people were all connected in some way with Dayton's murder, and it all began to point to Lankford and Marco.

The trial was set to begin in May 2013. However, when Haller went to FCI Victorville to visit Moya, his car was intentionally rammed by a tow truck. The Lincoln went off the highway, ejecting and killing Earl Briggs. Haller had more moderate injuries, but it resulted in the trial being delayed a month, to June 17. He was going up against prosecutor William Forsythe, before Judge Nancy Leggoe. Thanks largely to Cisco, Haller had some great evidence on his side. The trick was to get it admitted. His homerun ball was a video that Cisco had obtained showing Lankford and Marco breaking into a house and planting drugs. Using this video, he got Lankford to tell the whole truth on the stand, after which the investigator shot and killed himself in court. The charges against La Cosse were dismissed. Haller and La Cosse got a $2.4 million settlement which paid Haller for his work and enabled him to give $100,000 to Earl Briggs' mother. He also bought himself two new Lincoln Towncars.

During the trial Maggie and Hayley moved to Ventura County. Because he had defended an innocent man, Haller was able to reconcile with his daughter. The LA Times ran an in-depth article on the La Cosse case which gave a boost to Haller's ego and reputation. Haller and Kendall Roberts had become more serious. They took a trip to Hawaii together after the trial was over.

In 2014, after Bosch "retired", Haller represented him in a suit against the city for improper termination. In 2015, while Cisco was out of commission due to an injury, Haller asked Bosch to work on the case of Da'Quan Foster who was accused of murdering Lexi Parks. Haller was convinced that Foster was innocent but he had little evidence to support his belief. Haller did not know that he was being observed by two vice detectives, Ellis and Long. One night after he and Bosch had talked, Ellis and Long stopped him for DUI and in the process got a look at his file on Foster.

While Bosch was investigating, Haller focused on strengthening the defense case for Foster. There were several pieces of evidence that boosted Haller's case. Security video from Hollywood Forever Cemetery showed Foster going to Haven House motel on the night of the murder, bolstering his alibi. In addition, the DNA sample taken from Parks showed Condom Trace Evidence, suggesting a method by which the semen could have been planted. The deaths of Ellis and Long should have been enough to free Foster, but the D.A. chose to proceed with his trial. Haller filed an emergency 995 motion which is essentially a rehearing of the preliminary hearing. Bosch testified and Haller introduced the condom evidence. The judge dismissed the charges against Foster, making Haller a celebrity once more.

Daly actually told Connelly that "there is no client as scary as an innocent man," and the line became the epigraph (attributed to J. Michael Haller) of the Lincoln Lawyer. Haller's work method was based on a conversation that Connelly had with attorney David Ogden at Dodger Stadium, who worked out of the backseat of his car with a client as a driver.